Avalanche Forecast

Issued: Mar 15th, 2017 6:41PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Loose Wet.

mbender, Avalanche Canada

Purcells.

Continued precipitation Wednesday night into Thursday combined with moderate to strong southerly winds will continue to keep avalanche danger ratings elevated. A cautious approach is recommended in the coming days. Updated March 16 9:00am

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

THURSDAY: Cloudy with sunny breaks and scattered flurries through the day, accumulation 10cm overnight Wednesday into Thursday / Moderate southwest wind / Alpine temperature -7 / Freezing level: 1200mFRIDAY: Scattered clouds and flurries / Moderate south wind / Alpine temperature -6 / Freezing level 1200mSATURDAY: Flurries, accumulation 10-15cm / Moderate to strong southwest wind / Alpine temperature -2 / Freezing level 1600mMore details can be found on the Mountain Weather Forecast.

Avalanche Summary

It is expected that there was a widespread natural avalanche cycle on Wednesday. On Monday natural storm slabs to Size 2 were reported above 2400m on south and east aspects. On Sunday afternoon a rider-triggered Size 2.5 persistent slab avalanche was reported near Golden. Average slab depth was 50cm on a steep north facing aspect near 2300m. Additionally, several storm and persistent slab avalanches to Size 3 were also reported on Sunday - most activity was above 2300m on a variety of aspects.

Snowpack Summary

Around 60-90cm of new snow has fallen at upper elevations over the past several days and has been redistributed by light to moderate southerly wind. Warm temperatures on Sunday through Tuesday has resulted in moist and/or wet surface snow on all aspects up to 2100m. The new snow sits on top of faceted snow as well as isolated small surface hoar in sheltered areas and a thin sun crust on steep southerly aspects. The persistent weakness buried late-February is now down 70-120 cm, and is composed of weak facetted crystals on a thick rain crust as high as about 2000m and facets on sun crust on steep southerly aspects. This layer has produced easy results in recent snowpack tests and has proven especially reactive on steep southerly aspects. Several deeper persistent weaknesses also remain a concern, including surface hoar buried early-February and mid-January (primarily in the northern Purcells). The november crust and basal facets are still reactive in shallow, rocky start zones.

Problems

Storm Slabs

Weaknesses within and under the 20-50 cm of recent storm snow are susceptible to human triggering. These storm slabs are particularly deep and touchy on slopes loaded by southerly winds.

Be increasingly cautious as you transition into wind affected terrain.Be alert to conditions that change with elevation.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

Various persistent weaknesses strewn throughout the snowpack create the potential for large step-down avalanches. Warming is expected to increase the likelihood of these large avalanches, especially with cornice-fall triggers.

Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

Rain below 2000m has made the surface snow wet. As temperatures slowly cool there may still be the lingering possibility of triggering loose wet avalanches that step down to deeper weak layers.

Be cautious particularly where the debris flows into terrain traps.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 16th, 2017 2:00PM